The Triceps Brachii muscles are located on the back of the humerus and more commonly referred to as the triceps. They derive their name from a Latin phrase meaning “three headed arm muscle”, due to the fact that the triceps muscles have three muscle heads and therefore have three separate origin attachment points. These three heads are called the Lateral, Medial and Long and they connect the Humerus, Scapula to the Ulna. The Triceps Brachhii muscles are primarily responsible for the extension of the elbow joint (straightening of the arm). They are the largest muscles in the upper arms.
As with the Bicep muscle which has two heads and therefore two origin points, the Triceps muscles which has three heads has three different origin points. These origin attachment points are as follows;
1. The Long head arise from the lower part of the Glenoid Cavity which is a shallow depression on the scapula where the head of the Humerus fits. This head is responsible for giving the Triceps Muscle the horse shoe shape.
2.The Lateral head which arises from the upper half of the outside posterior surface of the humerus.
3.The Medial head which arises from the dorsal and inside posterior of the humerus and can usually only be visible closer to the elbow joint as it is mostly covered by the Lateral and Long heads.
These Three heads merge to form a single tendon which has an insertion attachment point at the Olecranon process which is the bony prominence of the elbow, on the upper ulna.
The main function of the Triceps muscles is as extensor muscles of the elbow joint, in other words muscles which contract to straighten your arm and as a result of this motion the triceps muscles are the antagonist of the biceps. There is also a secondary function of the Triceps muscles, which is only carried out by the Long head of the muscle and that is the adduction of the arm (bringing the arm closer to the mid-line of the body). This responsibility is shared with the Latissimus Dorsi.